Consciousness or the waking state is the condition in which active communication with the external world exists through the intermediation of the senses. It may undergo various modifications, some of a normal character, as in sleep, others of a morbid character, such as coma. During sleep, there is reason to believe, certain subconscious processes, partly of perception, partly of ideation, continue, and of which there is at times recollection and at other times none. This statement is exemplified in connection with dreams. In the derangements of consciousness symptomatic of morbid states, such as that which occurs, for example, in the course of epilepsy or of uremia, there is, as a rule, no memory of events that have transpired during this time. The dividing line between the normal and the abnormal, however, is at times so tenuous and the question of recollection or not is involved in so much uncertainty that